Old fashioned octopus
Here you see an old fashioned octopus hose carrying an old fashioned 2nd stage.
It is bulky, subject to free flowing, getting caught on objects underwater and malfunctioning in many ways.
It could fill with sand or mud. It had to be put your mouth in only one way. It could get tangled in your gear. You had to clear it before you could breathe.
Modern Air Buddy octopus
Here is the modern Air Buddy octopus. The working end is a miniature 2nd stage that is the same size as the low pressure hose. It will not free-flow, it cannot get caught on objects and its moving parts have been reduced in number and enlarged in size to a point where we can say it has yet to malfunction.
It does not have to be cleard. It will work properly any way you stick it in your mouth.